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    <title>用typeof查看数据类型</title>
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    <pre>
&lt;script type="text/javascript"&gt;
    alert(typeof 12345);	<span>//输出number</span>
    alert(typeof "abc");	<span>//输出string</span>
    alert(typeof document);	<span>//输出object</span>
&lt;/script&gt;
</pre>
    <script>
    alert("typeof 12345 → " + typeof 12345 + "\
	  \n\ntypeof \"abc\" → " + typeof "abc" + "\
	  \n\ntypeof document → " + typeof document);
    </script>
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